Intensity Interferometry at Southern Connecticut State University WORKING TOWARD THE INTERFEROMETER...
-
Upload
bertha-welch -
Category
Documents
-
view
218 -
download
0
Transcript of Intensity Interferometry at Southern Connecticut State University WORKING TOWARD THE INTERFEROMETER...
Intensity Interferometry at Southern Connecticut State UniversityWORKING TOWARD THE INTERFEROMETER
IN A SUITCASE
Elliott Horch,
Southern Connecticut State University
1
05.13.2014 HBT Workshop @ OCA
Collaborators
SCSU Undergraduates:Matthew Camarata, now at Boston UniversityA.J. Guerra
Gerard van Belle (Lowell Observatory)
Joe Ritter (University of Hawaii)
Russ Genet (CalPoly)
Bruce Holenstein (Gravic, Inc.)
05.13.2014 HBT Workshop @ OCA
2
Origins of Stellar Interferometry
1920’s: Albert Michelson builds first stellar interferometer by using two sub-apertures of Mt. Wilson 100-inch telescope.
Measured several stellar diameters.
Tried to extend the baseline, but mechanical issues prevented progress.
05.13.2014 HBT Workshop @ OCA
3
How Optical Interferometry is Done Today…
05.13.2014 HBT Workshop @ OCA
4
Light is made to interfere prior to detection. (Michelson Interferometry).
Higher signal-to-noise, but expensive. Certainly NOT portable.
~300 m baselines. Much Larger? Hmmm…
Intensity Interferomety There is a weak correlation in the
arrival times of photons when viewed by two different detectors. “Wave Noise.”
Related to beat frequencies, in the most extreme case.
This effect was used in astronomy in the 1970’s to measure diameters of bright stars.
One configuration of the two telescopes yields one Fourier component of the image
(well, |g|2).
But, huge collectors were needed to detect this weak signal on the photomultiplier tubes of the day.
5
Sydney University Stellar Interferometer
Photo: J. Davis
P.S.: Only two stations, So no imaging!
05.13.2014 HBT Workshop @ OCA
“Wave Noise”
05.13.2014 HBT Workshop @ OCA
6
A lot has changed since 1974!S/N in Intensity Interferometry depends on
telescope size AND speed of electronics.
Timing capabilities today are about 1000x what they were in the 70’s.
Can achieve the same result today with a much smaller telescope! (Portable Instrument!)
7
05.13.2014 HBT Workshop @ OCA
Simulation Data
05.13.2014 HBT Workshop @ OCA
8
Random Correlations
~| |g 2
Data “Frames” ~0.4 ms long(8192 elements)
Intensity Interferometry Revisited9
Picoquant Picoharp 300timing module.
Two SPAD detectors
Issues: Small size, dead time.
05.13.2014 HBT Workshop @ OCA
Truly Portable
05.13.2014 HBT Workshop @ OCA
10
53-m baseline
SPAD
Anderson Mesa(Lowell Observatory)
Perkins Telescope
Two runs: Dec 2011 & June 2012Issues: Focus, Sky Position, Temp.
Lowell Set-up and Data
05.13.2014 HBT Workshop @ OCA
11
Big Glass is getting cheap!
05.13.2014 HBT Workshop @ OCA
12
Three-Station Wireless Interferometer at SCSU
05.13.2014 HBT Workshop @ OCA
13
GPSComputer Cards:~0.5mssynchronization
Dirty Beam Simulation
05.13.2014 HBT Workshop @ OCA
14
FWHM ~ 0.1 mas uv-plane coverage6-hour observation
Kitt Peak: Another Possibility?
05.13.2014 HBT Workshop @ OCA
15
Mayall+WIYN(3.8m + 3.5m)~700m baseline
SPAD Arrays
Deadtime and small size can be mitigated if you have many SPADs all looking at the same source.
Development of SPAD arrays is being started, e.g. the SPADlab at Everyphotoncounts.com
05.13.2014 HBT Workshop @ OCA
16
Optics Package for an 8-channel station
05.13.2014 HBT Workshop @ OCA
17
Grating
Flat
Flat
Coll.Lens
Filter
Reimager
SPAD Array
Observation Time
05.13.2014 HBT Workshop @ OCA
18
Conclusions Intensity Interferometry Opportunity Today
We’ve got intereting instrumentation for intensity interferometry: SPADs, Picoharp
Large Dobsonian Telescopes are affordable for on-campus observing.
Need to explore GPS Technology/atomic clocks for wireless operation.
Take timing correlator and the SPAD detectors to larger telescopes. “Interferometer in a suitcase.” Lowell: Already doing this.
Kitt Peak: A possibility for the future.
Science: Imaging close binaries, stellar surfaces Imaging an exoplanet transit? (One fine day…)
19
05.13.2014 HBT Workshop @ OCA